To understand the mechanism of contractile process of the cleavage furrow, we propose to study (1) isolated cleavage furrow by biochemical methods, (2) immunohistochemical localization of contractile proteins in the furrow and (3) cell-free model system of the cleavage furrow. Immunohistochemical studies will be done at both light and electron microscopic levels, using antibodies against actin, myosin, alpha-actinin and other contractile proteins. Cell-free models will be made using sea urchin egg or tissue culture cells. Glycerination using stabilizing buffer will be attempted.